The present nonprovisional application claims priority under 35 USC 119 to Japanese Patent Application No. 2002-027457 filed on Feb. 4, 2002 the entire contents thereof is hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a jet propulsion boat of a type wherein a body of the boat is advanced by jetting a jet stream via a nozzle and the direction of the nozzle is changed by a steering system when the boat is turned right or left.
2. Description of Background Art
A jet propulsion boat acquires propulsion by jetting a jet stream and changes the direction of the body by changing the direction of the jet stream. Therefore, changing the direction of the boat is disabled without a jet stream.
Generally a human being, when he/she tries to avoid an obstacle for example, he/she is apt to reduce the speed of a boat and turn a steering handlebar to the right or left. The reduction in the speed means closing a throttle and as the output of an engine is small even if the steering handlebar is steered right or left in a state in which the throttle is closed, the jet stream is weak and the direction of the body cannot be changed as desired. This is more pronounced when the boat is particularly navigated at a high speed.
A technique for supplementing such a characteristic of the jet propulsion boat is disclosed in U.S. Pat. No. 6,159,059.
This technique enables a throttle regulator 46 to be prevented from being rapidly closed when a throttle lever 34 is released and a predetermined jet stream can be maintained for a while when the throttle lever 34 is returned by connecting one end of a throttle cable 44 to the throttle regulator 46, connecting the throttle lever 34 to the other end of the throttle cable 44, arranging a throttle return spring 49 for replacing the throttle lever 34 and arranging compressible material 52 at the base of the throttle lever 34 according to FIGS. 2 and 3 of U.S. Pat. No. 6,159,059.
However, after a while wherein the predetermined jet stream is maintained, an amount of the jet stream decreases and the turning performance is deteriorated. As a result, the operation of the boat is deteriorated.
FIGS. 7(a) to 7(c) are explanatory drawings showing an improved jet propulsion boat.
FIG. 7(a) is a graph showing a throttle angle under control, the y-axis shows a throttle angle xcex8 and the x-axis shows time. FIG. 7(b) is a graph showing engine speed under control, the y-axis shows engine speed Ne and the x-axis shows time. FIG. 7(c) shows the movement of the jet propulsion boat 100 under control.
As shown in FIG. 7(a), a throttle is once turned off and after predetermined time (between P101 and P102) elapses, a throttle angle xcex8 is set to xcex83. That is, auxiliary propulsion is generated between P102 and P103.
As shown in FIG. 7(b), when the body of the boat 100A shown in FIG. 7(c) is propelled, pressure in front of an impeller (not shown) is lower than pressure at the back and when the speed of the boat 100A is reduced, pressure in front of the impeller is higher than pressure at the back. Therefore, when the engine speed is increased to enhance the output of an engine during the reduction of the speed of the boat, an overshoot phenomenon S wherein the engine speed is held at a predetermined engine speed after the engine speed once increases up to the predetermined engine speed or higher occurs.
As shown in FIG. 7(c), a jet propulsion boat 100A that is navigated in a straight line generates an auxiliary propulsion at the time of the jet propulsion boat 100B, the engine speed is increased due to the overshoot phenomenon S and the boat may slide laterally to a great extent in a direction shown by an arrow 2 to the jet propulsion boat 100C.
That is, a jet propulsion boat that can maintain a suitable jet stream to turn the boat is desired.
It is an object of the present invention to provide a jet propulsion boat that closes a throttle when the boat is navigated at a predetermined speed or higher for securing a fixed turning performance even if a steering handlebar is steered right or left at a predetermined angle or more, that is, during deceleration.
To achieve the object of the present invention a jet propulsion boat of a type wherein an impeller is turned by an engine as a driving source is provided wherein a jet stream is generated by the impeller. The boat is advanced by jetting the jet stream via a nozzle and the direction of the nozzle is changed by a steering system when the body of the boat is turned to the right or left. A controller is provided for executing engine output control wherein a throttle is closed when the boat is navigated at a predetermined speed or higher and the output of the engine is gradually increased up to a predetermined output when a steering handlebar is steered to the right or left at a predetermined angle or more is provided.
When the throttle is closed and the steering handlebar is steered to avoid an obstacle which emerges in front of the boat, turning performance is deteriorated because the amount of the jet stream decreases. Then, the output of the engine is increased up to a predetermined output and the amount of a jet stream is increased under a fixed condition.
However, when the throttle is closed and the output of the engine is reduced for navigation at a lower speed such as entering a port, the engine speed is not required to be increased. As turning performance is in question, the output of the engine is not required to be increased when the steering handlebar is not steered.
Therefore, it is a prerequisite that the throttle is closed when the boat is navigated at a predetermined speed or higher and the steering handlebar is steered right or left at a predetermined angle or more.
When the boat is propelled, pressure in front of the impeller is lower than pressure at the back and when the boat is decelerated, pressure in front of the impeller is higher than pressure at the back. Therefore, when the engine speed is increased to enhance the output of the engine during deceleration, an overshoot phenomenon wherein the engine speed is held at a predetermined engine speed after the engine speed once increases up to the predetermined engine speed or higher occurs and the body of the boat may slide laterally to a great extent. Then, the controller that executes an engine control for gradually increasing the output of the engine up to a predetermined output is provided. As a result, the body of the boat can be prevented from sliding laterally to a great extent at the beginning of the turning.
The present invention includes a controller that is provided with plural engine control characteristics and the output control of the engine is executed by selecting the speed of the boat.
The engine output control characteristic matched with the speed of the boat can be used by providing plural engine output control characteristics to the controller and enabling selection depending upon the speed of the boat.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.